This invention relates broadly to a process and apparatus for the biological degradation of organic waste material into compost and more particularly to a process and apparatus for the microbial treatment of waste streams of essentially organic composition uncontaminated by inorganic materials. For optimum performance of the process it is important that material undergoing treatment be organically degradable, substantially uniform in composition and finely comminuted.
Farm waste, for example, meets the requirement of substantial uniformity in composition as do waste streams generated by fast-food chains, restaurants and other waste generating activities of more or less predictable nature. To achieve the degree of comminution thereby to accelerate the biological process the material is shredded prior to being introduced into the digester drum.
It should also be noted that the process and apparatus of this invention can also be utilized in the treatment of municipal solid waste when undesirable inorganic components of the waste stream are removed by presorting and the organic material itself is properly sized by first being passed through a shredder or other suitable mechanism before being introduced into the digester chamber.
By limiting the composting process to the treatment of waste material meeting the above qualifications a unique continuous feed digester of reduced size, cost and complexity can be employed as contrasted with the large size, relatively costly batch-treatment systems of the prior art as exemplified by U.S. Pat. Nos. 5,047,349 and 3,245,759 assigned to the assignee of the present invention.
It should be noted, for example, that present day techniques for handling farm waste are to windrow the material or to spread the raw organic material on the land. The former technique is both time consuming and an inefficient use of land and the latter technique is one coming under increasing scrutiny and regulation by the EPA as an environmentally unsound and possibly hazardous practice in that run off of such material into streams, ground water, and aquafirs could result in contamination of the potable water supply.
The present invention addresses these problems by providing an economic and expeditious process and apparatus for converting organic waste streams such as described above into a rich humus or compost which after treatment meets the vector attraction and pathogen reduction requirements of a class one product as currently defined by the EPA.